// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_BASE_VIDEO_RENDERER_SINK_H_
#define MEDIA_BASE_VIDEO_RENDERER_SINK_H_

#include "base/logging.h"
#include "base/memory/ref_counted.h"
#include "base/time/time.h"
#include "media/base/media_export.h"
#include "media/base/video_frame.h"

namespace media {

// VideoRendererSink is an interface representing the end-point for rendered
// video frames.  An implementation is expected to periodically call Render() on
// a callback object.
class MEDIA_EXPORT VideoRendererSink {
public:
    class RenderCallback {
    public:
        // Returns a VideoFrame for rendering which should be displayed within the
        // presentation interval [|deadline_min|, |deadline_max|].  Returns NULL if
        // no frame or no new frame (since the last Render() call) is available for
        // rendering within the requested interval.  Intervals are expected to be
        // regular, contiguous, and monotonically increasing.  Irregular intervals
        // may affect the rendering decisions made by the underlying callback.
        //
        // If |background_rendering| is true, the VideoRenderSink is pumping
        // callbacks at a lower frequency than normal and the results of the
        // Render() call may not be used.
        virtual scoped_refptr<VideoFrame> Render(base::TimeTicks deadline_min,
            base::TimeTicks deadline_max,
            bool background_rendering)
            = 0;

        // Called by the sink when a VideoFrame previously returned via Render() was
        // not actually rendered.  Must be called before the next Render() call.
        virtual void OnFrameDropped() = 0;

        virtual ~RenderCallback() { }
    };

    // Starts video rendering.  See RenderCallback for more details.  Must be
    // called to receive Render() callbacks.  Callbacks may start immediately, so
    // |callback| must be ready to receive callbacks before calling Start().
    virtual void Start(RenderCallback* callback) = 0;

    // Stops video rendering, waits for any outstanding calls to the |callback|
    // given to Start() to complete before returning.  No new calls to |callback|
    // will be issued after this method returns.  May be used as a means of power
    // conservation by the sink implementation, so clients should call this
    // liberally if no new frames are expected.
    virtual void Stop() = 0;

    // Instead of using a callback driven rendering path, allow clients to paint a
    // single frame as they see fit without regard for the compositor; this is
    // useful for painting poster images or hole frames without having to issue a
    // Start() -> Render() -> Stop(). Clients are free to mix usage of Render()
    // based painting and PaintSingleFrame().
    virtual void PaintSingleFrame(const scoped_refptr<VideoFrame>& frame,
        bool repaint_duplicate_frame = false)
        = 0;

    virtual ~VideoRendererSink() { }
};

} // namespace media

#endif // MEDIA_BASE_VIDEO_RENDERER_SINK_H_
